Technical Field
The present invention relates to a high density redistribution film prepared for IC package. Especially for a low profile IC package which has a single redistribution layer as a package substrate without using-an interposer.
Description of Related Art
FIG. 1 show a prior art
FIG. 1 shows a prior art U.S. Pat. No. 8,269,337 which discloses an IC package. The IC package comprises an IC chip 27 mounted on a top of a package substrate. The package substrate includes an interposer 21, a top redistribution layer 213 configured on top of the interposer 21, and a bottom redistribution layer 24 configured on a bottom of the interposer 21. A width of the bottom redistribution layer 24 is greater than a width of the interposer 21. A molding compound 22 wraps the top redistribution layer 213 and the interposer 21. Due to the tendency of miniaturization for IC package, an even thinner package has been pursued in the IC package technology for a long time.
A typical thickness for each layer of the IC package as shown in FIG. 1 is as follows:
L1=4 um, for the top first circuit layer fabricated according to IC process;
L2=8 um, for the top second circuit layer fabricated according to IC process;
L3=100 um, for the interposer 21;
L4=8 um, for the bottom first circuit layer fabricated according to IC process;
L5=40 um, for the bottom second circuit layer; fabricated according to PCB process; and
L6=40 um, for the bottom third circuit layer; fabricated according to PCB process. A total thickness is 200 um for the package substrate on bottom of the IC chip 27.